SEER is an authoritative source of information on cancer incidence and survival in the United States. SEER currently collects and publishes cancer incidence and survival data from population-based cancer registries covering approximately 28 percent of the U.S. population.

Adjusted AJCC 6th ed. T, N, M, and Stage

This project attempts to maximize the number of years that AJCC 6th ed. stage data are available for the analyses of long term trends in
incidence and survival. Derived AJCC 6th ed. T, N, M and Stage data exist for 2004+ based on information collected under Collaborative Stage (CS) and processed through the AJCC 6th ed. CS algorithm. This project
analyzes earlier extent of disease (EOD) information collected from 1988 to 2003 to determine which sites and years can be collapsed into the same AJCC 6th ed. definitions. Whenever there is an attempt to retrofit something there are assumptions that need to be made. This is an attempt to
document the assumptions and to make the data analyst aware of some pitfalls when using this type of information. These new recoded variables will be
referred to as Adjusted AJCC 6th ed. T, N, M, and Stage variables in order to distinguish them from the Derived AJCC variables.

Large differences in T, N, M or stage distributions between 1997 and 1998 OR 2003 and 2004 may be due to major changes in coding structures or rules.
Overall changes in better diagnostic procedures may contribute to decreases in TX Adjusted, NX Adjusted, MX and unknown stage.

Site Recode vs. Schema

Most users of SEER data use the SEER site recode to select cases for analysis of a particular site. For analyses of AJCC 6th stage in
SEER*Stat, ‘CS schema - AJCC 6th Edition’ should be used instead. For analysis of CS Site-specific factor (SSF) data, the
appropriate CS schema recode should be used e.g., as ‘CS schema v0204’ for analyses of 2010 Site-Specific Factor (SSF) data.

Breast - Adjusted AJCC Stage (1988+)

While AJCC 6th ed. can be either a clinical or pathologic stage, CS uses only best stage. Best stage uses the most informative information
from both the clinical and pathologic information. EOD (1988-2003) also uses a combination of path and clinical information.

NA (not applicable) is not an AJCC stage category. It is used as a placeholder for histologies that AJCC does not stage. For many solid tumors,
sarcomas are not staged. Excluding AJCC 6th ed. stage = NA is the easiest way to exclude the histologies that AJCC does not provide a stage.
Sub-categories of stage may have been eliminated if they were inconsistent between EOD and CS or couldn’t be defined for EOD (e.g. Stage IA, IB, IC
may be collapsed to Stage I).

T and N codes for unknown stage: after the AJCC 6th ed. algorithm was applied to EOD and CS data, the T and N codes were set to TX Adjusted and NX Adjusted, respectively for any case that mapped to unknown stage.

Breast - Adjusted AJCC T (1988+)

TX Adjusted decreases for most schemas over time. In addition to the overall drop, there also seems to be more of a drop between 2003 and 2004 when CS
started. TX Adjusted decreases over time and other categories show increases that are artifacts of the decrease in TX Adjusted.

Several schemas use size in addition to extension to determine the T code. The size category for 2004+ has additional categories to try to classify
cases which don’t have specific size information such as ‘stated as T1.’ Therefore, more cases in 2004+ may be able to go to a specific T
category than cases before 2004 (e.g., Breast, Lung and Kidney all use tumor size to derive T).

‘Any T with Mets’ is not an AJCC 6th T category but it was developed because earlier cases with M1 based on extension went to TX
M1 and the actual T category was lost. In order to make the definitions similar, the M1 cases for 2004+ based on extension were removed from the
individual T category and placed in ‘Any T with Mets’. Since these are all M1 cases, it did not change the stage classification.

Sub-categories of T may have been eliminated if they were inconsistent between EOD and CS or couldn’t be defined for EOD (e.g. T1a, T1b, T1c may
be collapsed to T1).

TX Adjusted: TX Adjusted is a combination of TX plus all unstaged cases. For the unstaged cases, there was a disconnect between EOD and CS cases in that CS cases could have a known T and N with an MX, whereas, EOD cases had to have at least one unknown (TX or NX). Another way to look at it, is that for CS (2004+), MX was coded independent of the T value and N value.

The T categories (T0, T1, T2, etc.) don’t exist for cases that stage to unknown or the M1 equivalent to stage usually Stage IV. The T category is NX Adjusted if the information maps to stage unknown - see TX Adjusted.

If the T and N categories are needed for cases with AJCC 6th ed. unknown stage, use the ‘Derived AJCC T, 6th ed (2004+)’ and ‘Derived AJCC N, 6th ed (2004+)’ variables which are only available for 2004+.

Breast - Adjusted AJCC N (1988+)

NX Adjusted decreases for most schemas over time. In addition to the overall drop there also seems to be more of a drop between 2003 and 2004 when CS
started. Whenever there is a drop in one category, there is a subsequent increase in one or more other categories. NX Adjusted decreases over time and other
categories show increases that are artifacts of the decrease in NX Adjusted.

‘Any N with Mets’ is not an AJCC 6th N category but it was developed because EOD cases with M1 based on lymph nodes went to
NX M1 and the actual N category was lost. In order to make the definitions similar, the M1 cases for 2004+ based on lymph nodes were removed from the
individual N category and placed in ‘Any N with Mets’. Since these are all M1 cases, it did not change the stage classification.

Many times the N category in AJCC 6th is more complicated than the simple codes used in EOD. We have tried to make it as comparable as
possible. One problem is that EOD does not include all combinations of the regional node categories and does not separate clinical from pathologic
information. Other issues include that subcategories for N0, N1, N2 and N3, may be available in the derived AJCC 6th N code but for
comparability to EOD data, the subcategories may have to be folded into the main N categories N0, N1, N2 and N3 when only these categories are
available for 1988-2003. This was only done when the specific sub categories for N0, N1, N2, or N3 are not used to determine stage.

Sub-categories of N may have been eliminated if they were inconsistent between EOD and CS or couldn’t be defined for EOD (e.g. N2a and N2b may be
collapsed to N2).

NX Adjusted: NX Adjusted is a combination of NX plus all unstaged cases. For the unstaged cases, there was a disconnect between EOD and CS cases in that CS cases could have a known T and N with an MX, whereas, EOD cases had to have at least one unknown (TX or NX). Another way to look at it, is that for CS (2004+), MX was coded independent of the T value and N value.

The N categories, N0, N1, etc. don’t exist for cases that stage to unknown or the M1 equivalent to stage usually Stage IV; the N category is NX Adjusted if the information maps to stage unknown - see NX Adjusted.

If the T and N categories are needed for cases with AJCC 6th ed. unknown stage, use the ‘Derived AJCC T, 6th ed (2004+)’ and ‘Derived AJCC N, 6th ed (2004+)’ variables which are only available for 2004+.

Breast - Adjusted AJCC M

MX decreases for most schemas over time. In addition to the overall drop there also seems to be more of a change between 2003 and 2004 when CS
started, and some of this may be due to the fact that MX is coded independent of T or N for CS but not for EOD. MX may also show a decrease and an increase in M0 around 2010 as medical practitioners and cancer registrars became aware that in the next version of AJCC cases of MX
are considered M0 for staging purposes.

Recording ‘no distant metastases’ have changed over time leading to a steady increase in M0 and subsequent decrease in MX, which has
resulted in more cases being staged. These changes cannot be resolved between EOD and CS. Caution is advised when comparing M0 and MX over time.

EOD 1988-2003

The SEER program has collected extent of disease information since 1975. The EOD information collected in 1983-1987 was very limited and isn’t
sufficient to collapse into the AJCC 6th ed categories. Over the period, 1988-2003, there were several revisions with the most major being for
cases diagnosed 1998-2003 when an attempt was made to make the EOD information collapsible to the AJCC 5th ed. Documentation for the codes and
coding structures used between 1988-2003 can be found in the Historical Staging and Coding Manuals. Some of the CS
fields include size, extension, lymph nodes, # LN positive, # lymph nodes. There isn’t a separate metastases field were recorded in the extension or
lymph node field There was also a major revision for prostate cancer in 1994 and 1995.

Collaborative Stage (CS) 2004+

CS started in 2004 and contained enough information to be collapsible to the AJCC 6th ed, summary stage 77 and 2000, and the SEER historical
stage.

Some of the CS fields include size, extension, lymph nodes, mets, # regional lymph nodes positive, # regional lymph nodes examined in addition to
evaluation (eval) fields to capture the basis of the information used for T, N, and M and additional SSFs which may or may not contribute to the
calculation of T, N, M, or stage.

There were several revisions but the major revision was for CSv2 in 2010 when CS was expanded to be collapsible to AJCC 7th ed. and
several additional SSFs were added for data collection depending on the revision.